Sulfation on a positive electrode and a negative electrode of a lead-acid battery is known as one reason of degrading the performances of the lead-acid battery. The sulfation occurs on both the electrodes by the following electrochemical reactions of a diluted sulfuric acid electrolyte solution with the positive electrode (lead oxide electrode) and with the negative electrode (lead electrode) during operation (discharging) of the lead-acid battery. The electrochemical reactions proceed in the reverse direction during charging:PbO2+4H++SO42−+2e−→PbSO4+2H2O(positive electrode)Pb+SO42−→PbSO4+2e−(negative electrode)
Sulfation (lead sulfation) on the surfaces of the positive electrode and the negative electrode (electrode surfaces involved in charging) interferes with the desired electrochemical reactions between the respective electrodes and the electrolyte solution and thereby degrades the charging performance and the discharging performance of the lead-acid battery.
Application of a pulse current to the lead-acid battery is known as the technique of recovering the performances of the lead-acid battery, which are degraded by sulfation.
This known technique takes account of reduction of performance degradation of the lead-acid battery during discharging but does consider removal of sulfation on the electrodes of the used lead-acid battery or recovery of performances of the lead-acid battery. This known technique also does not take account of shortening a period of time required for removal of sulfation or reducing a temperature increase of a removal apparatus during removal of sulfation.
There is accordingly a requirement to shorten a period of time required for removal of sulfation, while reducing heat regeneration during removal of the sulfation in the lead-acid battery.